It preceded the 9/11 incident.Ī key vulnerability in the User Segment is that a GPS receiver has to cope with very low powered signals received from the satellite.įig. The US Department of Transport’s Volpe National Transportation Systems Center studied how vulnerable a transportation infrastructure reliant on GPS would be. A mariner who has relied on electronic navigation at sea and has experienced equipment failure knows only too well the importance of maintaining proficiency in traditional navigational skills. In navigation, traditional skills are set to become an important secondary method. To overcome this, a user should be prepared for when GPS experiences problems. People dismissing potential problems and becoming over-reliant on GPS. Similarly, a small mistake at the User Segment can result in a positioning error of up to 1 m whereas a large mistake can result in a positioning error of anything up to hundreds of meters. These could occur in any segment be it ground, space, or user.Ī small mistake at the Ground Segment by either a computer or a human can result in a positioning error of up to 1 m whereas a large mistake can result in a positioning error of anything up to hundreds of kilometers. (b)īlunders due to errors in the design, or implementation, of hardware or software. A blunder can result in a positioning error of anything up to hundreds of kilometers:īlunders caused by human factors such as GPS employees or users lacking the requisite knowledge or training. Improvements in antenna design have significantly reduced these errors. These depend on the antenna type and placement of the antenna. RFI interference in the form of harmonics, caused by external sources. Spectrum competition which could result in congestion, causing radio-frequency interference (RFI). Only a small number of frequencies are used (today’s GPS makes use of a single one for general use) and the signal structure is known by all. A receiver receives very low powered signals which means that a high-powered signal could saturate the receiver.